The phenomenon of muscle migration in growing bones is of potential importance in orthopedic medicine and in developmental biology and evolutionary morphology. Yet it is an almost untouched research area. The work proposed in this application is designed to elucidate the control factors involved in muscle migration. Work that has been completed has shown that during growth muscles maintain constant linear positional relationships to the end of the bone to which they are attached and that for each unit the bone grows the muscle migrates some constant proportion of that distance. Work currently in progress seems to indicate that paralysis of the muscle does not affect migration but that cessation of growth at the nearest growth plate does hinder migration. We are tentatively hypothesizing that the growth plates of the bones in some way control migration of nearby muscles. Transplantation experiments have shown that there is only a small area around the normal position of attachment in which the newly transplanted muscle will respond by migrating. Transplantation greater distances away result in no migration or immigration in the wrong direction. The work proposed herein will extend these observations and hopefully allow us to propose some testable hypotheses as to the identification of the factors controlling muscle migration.